1、Designation: E2248 15Standard Test Method forImpact Testing of Miniaturized Charpy V-Notch Specimens1This standard is issued under the fixed designation E2248; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes notched-bar impact testing ofmetallic materials using Miniaturized Charpy V-Notch(MCVN) specimens and
3、 test apparatus. It provides: (a)adescription of the apparatus, (b) requirements for inspectionand calibration, (c) safety precautions, (d) sampling, (e) dimen-sions and preparation of specimens, (f) testing procedures, and(g) precision and bias.1.2 This standard concerns Miniaturized Charpy V-Notch
4、specimens, for which all linear dimensions, including lengthand notch depth, are reduced with respect to a type A standardimpact test specimen in accordance with Test Methods E23.These are not the same as sub-size specimens, described inAnnex A3 of Test Methods E23, for which length, notch angleand
5、notch depth are the same as for the standard typeACharpyspecimen. See also 1.5 below.1.3 Comparison of the MCVN data with conventionalCharpy V-Notch (CVN) data or application of the MCVN data,or both, to the evaluation of ferritic material behavior is theresponsibility of the user of this test metho
6、d and is notexplicitly covered by this test method.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not address testing of sub-sizespecimens as discussed in Test Methods E23. The readershould understand
7、 the distinction between miniature and sub-size. Miniature specimens are shorter that sub-size specimensso that more tests can be conducted per unit volume ofmaterial. Moreover, miniature specimens are designed so thatthe stress fields which control fracture are similar to those ofconventional Test
8、Methods E23 specimens.1.6 The MCVN test may be performed using a typical TestMethods E23 test machine with suitably modified anvils andstriker or using a smaller capacity machine.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
9、sibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsE23 Test Methods for
10、 Notched Bar Impact Testing of Me-tallic MaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE2298 Test Method for Instrumented Impact Testing ofMetallic Materials2.2 ISO Sta
11、ndards:3ISO 148 Metallic materials - Charpy pendulum impact test- Part 1: Test methodISO 14556 Steel - Charpy V-notch pendulum impact test -Instrumented test method3. Summary of Test Method3.1 The essential features of the MCVN impact test are: (a)a suitable miniature three point bend specimen, (b)
12、anvils andsupports on which the test specimen is placed to receive theblow of the moving mass, (c) a moving mass (striker) that hasbeen released from a sufficient height to cause the mass tobreak the specimen placed in its path, (d) a device fordetermining the energy absorbed by the broken specimen,
13、 andoptionally (e) instrumentation for measuring applied force as afunction of time during specimen loading (refer to Test MethodE2298).1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.07 onImpact Testing.Curr
14、ent edition approved Oct. 1, 2015. Published December 2015. Originallyapproved in 2009. Last previous edition approved in 2013 as E224813. DOI:10.1520/E2248-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
15、 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.org.*A Summary of Changes section appears
16、at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 The test consists of breaking the miniaturized specimen,notched in the middle, and supported at each end, with oneblow from a swinging pendulum under condi
17、tions definedhereafter.4. Significance and Use4.1 There are cases where it is impractical or impossible toprepare conventional CVN specimens. MCVN specimens arean alternative approach for characterizing notched specimenimpact behavior. Typical applications include MCVN speci-mens prepared from the b
18、roken halves of previously testedspecimens, from thin product form material, or from materialcut from in-service components.4.2 This standard establishes the requirements for perform-ing impact tests on MCVN specimens fabricated from metallicmaterials. Minimum requirements are given for measurementa
19、nd recording equipment such that similar sensitivity andcomparable measurements, as compared to conventional CVNtests, are achieved. The user should be aware that the transitionregion temperature dependence data obtained from MCVNspecimens are not directly comparable to those obtained fromfull-size
20、standard Charpy-V specimens and suitable correlationprocedures have to be employed to obtain ductile-to-brittletransition temperature (DBTT) data equivalent to those ob-tained using CVN specimens. In all instances, correlations willhave to be developed to relate upper shelf energy (USE) datafrom MCV
21、N test to CVN comparable energy levels. Applica-tion of MCVN test data to the evaluation of ferritic materialbehavior is the responsibility of the user of this test method.MCVN test data should not be used directly to determine thelowest allowable operating temperature for an in-service ma-terial. T
22、he data must be interpreted within the framework of afracture mechanics assessment.4.3 While this test method treats the use of an instrumentedstriker as an option, the use of instrumentation in the impacttest is recommended and is fully described in Test MethodE2298. In order to establish the force
23、-displacement diagram, itis necessary to measure the impact force as a function of timeduring contact of the striker with the specimen. The area underthe force-displacement curve is a measure of absorbed energy.As an alternative, absorbed energy may be evaluated directlyfrom machine dial reading. Wh
24、enever possible, an opticalencoder shall be used in place of the machine dial because anencoder has better resolution than a dial.5. Test Machine5.1 The test shall be carried out with a pendulum-typeimpact testing machine which is (optionally) instrumented todetermine force-time curves. The test mac
25、hine shall havesufficient capacity to break the specimen in one blow whilelosing not more than 80 % of the initial potential energy.Provided energy measurements can be obtained with a resolu-tion better than or equal to 0.1 J, the same test machine used forCVN testing may be used to test MCVN specim
26、ens.5.2 The MCVN specimen has to be suitably supported sothat the centerline of the specimen coincides with the center ofstrike of the pendulum. If the same machine used for CVNtesting is used for MCVN specimens, refer to Appendix X3 ofE23 for changing the specimen support height by manufactur-ing n
27、ew supports or adding shims.5.3 The impact velocity (tangential velocity) of the pendu-lum at the center of the strike shall not be less than 1 nor morethan 6 m/s.NOTE 1Impact velocities above 4 m/s are not advisable for instru-mented MCVN tests, since excessive oscillations are then superimposedon
28、the initial portion of the test diagram and errors in the evaluation of theforce-displacement trace may occur. For the same reason (ease ofinterpretation of the instrumented curve), lower velocities are allowed forMCVN tests than required by E23 (not less than 3 m/s).5.4 It is recommended that the s
29、calability of the stress fieldsis maintained. This is accomplished by scaling the strikerradius, anvil radii, and the span of the anvils with respect to aspecimen size that is proportional to the CVN specimen. Fig. 1shows the dimensions of 8 and 2 mm strikers (3.86 mm and0.96 mm) scaled for use with
30、 the nominal12-scale MCVN(4.83 by 4.83 by 24.13 mm) specimen shown in Fig. 2. ForFIG. 1 Scaled 8 mm and 2 mm Strikers for Use in Miniaturized Charpy Impact TestingE2248 152both of these scaled strikers, the anvil radius is scaled to 0.48mm 6 0.025 mm, and the span is 19.3 mm 6 0.025 mm.5.5 A non-sca
31、led 2 mm striker can be used to test the 4 by3 by 27 mm MCVN specimen described in Annex D of ISO14556. The anvil radius and span, in this case are 10+0.50mmand 220+0.10mm respectively.NOTE 2This particular test is allowed because a substantial amount ofdata exists for this specimen and test geometr
32、y. This MCVN specimen isnot proportional to the CVN specimen, so scaling is not appropriate.5.6 The testing machine shall be a pendulum type of rigidconstruction. All general requirements for apparatus and cali-bration specified in Test Methods E23 shall be satisfied.5.7 For instrumented force measu
33、rements using optionalforce measuring instrumentation, the requirements given inTest Method E2298 regarding striker instrumentation, dataacquisition, and data analysis shall be satisfied.6. Hazards6.1 Safety precautions should be taken to protect personnelfrom electric shock, the swinging pendulum,
34、flying brokenspecimens, and hazards associated with specimen warming andcooling media. See also 1.6.7. Test Specimens7.1 The recommended proportional specimen configurationis the square cross section notched bar shown in Fig. 2. Thecross sectional dimension is slightly under 5 mm to enablemachining
35、from a previously tested CVN. Information onadditional specimen geometries that have been successfullyused is provided in Appendix X1.NOTE 3In case MCVN specimens are extracted from broken CVNspecimens of highly ductile materials, the user should ensure that thesevere plastic deformation occurred du
36、ring fracture of the CVN specimensdoes not affect the impact behavior of the miniaturized samples.7.2 Microstructural considerations dictate that only V-notchspecimens with cross sectional dimensions sufficient to ensurea representative volume of material is tested may be used. Inorder to satisfy th
37、is requirement, the size scale and meanseparation distance of inhomogeneities that exist in the mate-rial must be known. The cross sectional dimension must be atleast five times greater than the largest inhomogeneity. Post-test metallography may be performed in order to confirm thatthe requirement h
38、as been met.7.3 Stress field similitude dictates that if the miniaturizedspecimens (such as the one shown in Fig. 2) do not satisfy themicrostructural considerations, specimens with a larger crosssection may be used. For the square cross section specimen inFig. 2, all the remaining specimen dimensio
39、ns (length, notchdepth, etc.) shall be scaled by appropriate ratio with theconventional CVN dimensions. This has the advantage ofstandardization of approach and scalability of previouslycalculated finite element solutions.7.4 Machining the outside surfaces of the MCVN specimensusing continuous wire
40、electric discharge machining (EDM) orany other machining method which produces less than 0.005NOTE 1Permissible variations shall be as follows:Angle of striker 1Radius of curvature of striking edgeNominal 1 mm Striker: +0.25, 0 mmNominal 4 mm Striker: 0.025 mmRadius of shoulder of nominal 4 mm strik
41、er 0.025 mmWidth of edge of nominal 4 mm striker 0.025 mmSurface finish requirements 0.1m or betterNotch length to edge 90 2Notch root radius 0.025 mmAdjacent sides at 9010minLigament length 0.025 mmCross section dimensions 0.025 mmFinish requirements2m notched surface/opposite surface4m other surfa
42、cesLength of specimen +0, -0.12mmCentering of notch 0.12 mmAngle of notch 1FIG. 2 Nominal12-Scale Miniaturized Charpy Impact SpecimenE2248 153mm of disturbed material on the surface is acceptable (1). Thecrack starter notch shall be EDM machined or precisionground.7.5 Side grooving of the MCVN speci
43、mens (see also Ap-pendix X2) is optional. Investigations (see Appendix X2) haveshown that the use of side grooves on MCVN specimensprovides a larger volume of material which is sampled at planestrain conditions. This results in less downward shift intemperature due to loss of constraint caused by mi
44、niaturization,and thereby reduces the need for correction factors to simulateCVN transitional fracture temperature dependence.7.6 The choice of specimen depends on the application.NOTE 4Although this test method specifically addresses impact testsperformed on notched specimens, the use of unnotched
45、samples may beadvantageous when testing refractory metals or materials produced bypowder metallurgy methods. For such materials, machining an accuratenotch without producing significant damage is extremely difficult. The useof unnotched specimens, however, is outside the scope of this test method.7.
46、6.1 For some materials, the use of different methods formachining specimens may increase results variability and datascatter. For this reason, the machining method used shall bereported (see 11.1.2). Performing microstructural investiga-tions in order to determine the depth of the recast layer might
47、be helpful.8. Test Procedure8.1 The test procedure may be summarized as follows: thetest specimen is heated/cooled in situ (that is, at the impactlocation) or it is removed from its cooling (or heating) medium,and positioned on the specimen supports; the pendulum isreleased with minimum vibration; a
48、nd the absorbed energy isrecorded from the machine dial or, preferably, from the opticalencoder. For instrumented tests, the force-time curve is mea-sured and evaluated to give the total absorbed energy.8.2 The temperature of the specimen at impact must bewithin 62C of the nominal test temperature.
49、Due to the smallsize of the specimen, in tests below or above room temperature(RT), special attention must be devoted to temperature controlwithin the above mentioned tolerance. It is recommended thatin-situ heating/cooling be used. If a bath transfer system isused, it will be necessary to transfer the specimen to thesupports and strike the specimen within a very short period oftime (1sorless). If a thermal bath transfer system is notused, dummy specimens (with internal thermocouples) or testspecimens (with surface thermocouples) shall be used
